Investors began selling shares after a report of a fuel leak from a Dreamliner at Boston’s Logan International Airport. The flight, operated by Japan Airlines, had 178 people on board and returned safely to the terminal after the leak was spotted.

It’s the second day in a row that a JAL 787 had problems in Boston. On Monday, a fire broke out on an empty Dreamliner that had just arrived from Tokyo. The fire was in the left electrical equipment bay, which is the same place in which a fire erupted on a United Airlines 787 enroute to Newark from Houston last month, prompting the plane to make an emergency landing in New Orleans. The cause of the fires hasn’t been determined. No one was injured in either incident.

The Dreamliner woes come as Boeing is working through a backlog of orders for almost 800 of the jetlines, the Wall Street Journal reported. The Dreamliner’s electrical systems are more complicated than many earlier commercial aircraft.

As the Journal noted:

The 787 was designed for long over-water routes between midsize cities that couldn’t profitably accommodate a larger jet with more seats. It has had to meet a stringent set of regulations to ensure the jet can still fly safely in the event one of its two engines fail.

Those regulations include strict guidelines for the lithium ion batteries on the 787 because of concerns about the batteries’ potential flammability.

During the 787’s development, Boeing repeatedly affirmed that it complied with the expanded safety standards for the batteries, which are part of the aircraft’s emergency power system.

Safety concerns about lithium ion batteries as cargo recently prompted some airlines to begin isolating shipments and enhancing fire suppression. The batteries are suspected of contributing to two jumbo-jet 747 freighter crashes since 2010.

The 787, the first jetliner made from a majority of lightweight carbon fiber composites, eliminates hot, heavy and hard-to-maintain pneumatic systems that power key parts of the jet.

Boeing’s design is considered “more-electric,” controlling parts of the aircraft such as the starting of the engines to the anti-ice system.

Aircraft launches can be problematic. Commercial jets are, after all, complex machines with more than a million individual parts, and it takes a while for all the bugs to get worked out. But the problems with the 787 have been highly visible and potentially dangerous. Investors clearly are worried that if the problem persist, the Dreamliner could become a nightmare for Boeing.